1. Technical Field
The disclosure relates to a network signal receiving system and a network signal receiving method.
2. Description of the Related Art
The high definition multimedia interface (HDMI) version 1.4 has a new function named HDMI Ethernet and Audio return Channel (HEAC), where the HEAC function can make a network receiver to transmit/receive HDMI Ethernet Channel (HEC) data signals and Audio Return Channel (ARC) data signals simultaneously. Therefore, complex home network wiring can be simplified to provide a single high bandwidth and high-quality wiring in order to transfer complete images, audios, and Ethernet transmission, and achieve integration of multimedia networking applications.
In the HDMI device having HEAC function, both the HEC data and the ARC data are transmitted via two transmission cables, where the transmitted HEC data signal is a differential mode signal, and the transmitted ARC data signal is a common mode signal, as shown in FIG. 1. Ideally, an impedance of each of the two transmission cables should be 50 ohm that is defined in the HDMI specification, and the differential mode signal (i.e. the HEC data signal) can be obtained by calculating a difference between two signals of the two transmission cables at receiving ends to cancel the common mode signal (i.e. the ARC data signal).
However, if two transmission cables (TX+, TX−) utilized for transmitting the HEC data signals and the ARC data signals have poor quality, the performance and quality of the HEC data signals will be affected. For example, when the two transmission cables have different impedances, or the impedances of the two transmission cables do not match the impedances of the receiver, the amplitudes of two-halves of the received common mode signals will be different, as shown in FIG. 2. The two-halves of the common mode signal having different amplitudes will make the obtained differential mode signal have noises, and seriously reduce the performance and quality of the HEC data signals. In addition, when the two transmission cables have different delay times (i.e. a phase mismatch is existed between two signals of the two transmission cables), the phases of two-halves of the received common mode signals will be different, as shown in FIG. 3. The two-halves of the common mode signal having different phases will also make the obtained differential mode signal have noises, and seriously reduce the performance and quality of the HEC data signals.